Summary The neurotensin system has attracted a lot of attention as a potential target to treat drug addiction due to its ability to modulate dopamine signaling and transmission. However, despite extensive effort by the pharmaceutical industry and academia over the past 30 years, there are still no potent, selective NTSR1 non- peptide agonists or potentiators and only a few antagonists described in the literature. From a high throughput screening (HTS) perspective most of the attention has been paid to interactions between the NTSR1 receptor and its signaling through the Gq protein-coupled signal transduction pathway. However, it is now clear that NTSR1 can couple to multiple G proteins and may even signal in a G-protein independent fashion. Hence, the overall goal of this proposal is to employ a multiple assay approach to drive an iterative medicinal chemistry program aimed at identifying potent, selective, cell penetrant positive modulators of NTSR1. To avoid missing potential valuable compounds our approach is to screen compounds in multiple cell-based assays with different functional readouts. This can be viewed as casting a wide net to capture compounds that modulate the receptor via different mechanisms and then letting the efficacy in the functional assays enable us to create a cellular response profile or 'functional fingerprint' for each compound. This in vitro functional fingerprint will be invaluable for future evaluation of compounds in vivo, the challenge being to identify physiological consequences of functional selectivity at NTSR1. Thus, our multiple assay approach is a vast improvement over the single [Ca2+]/FLIPR assay approach typically pursued by the pharmaceutical industry.